The present invention is related to a bicycle front end assembly, and more particularly, to an aerodynamically shaped front end of the bicycle.
In prior art bicycles, the fork and handlebar are attached to a head tube of the bicycle frame via a threaded headset (see FIG. 1) or a non-threaded headset (see FIG. 2). In relation to threaded headsets, the fork may comprise a steerer shaft which protrudes upwardly from a fork crown which joins fork legs. The steerer shaft is sized and configured to be received within the head tube of the frame. A lower bearing is interposed between the lower end portion of the head tube and the fork crown. Also, an upper bearing is interposed between the upper end portion of the head tube and an upper cone or cup which is attached to the upper end portion of the head tube. The upper and lower bearings allow the fork to pivot about the head tube of the bicycle frame.
The handlebar stem is inserted into the steerer shaft. The handlebar stem has a lower quill that frictionally engages the wedge. The handlebar stem and the steerer shaft are engaged to each other via a compression bolt. The compression bolt is insertable through the handlebar stem and threadably engagable to an internal thread of the quill. The compression bolt expands the quill and wedge to fixedly attach the handlebar stem and fork. After the handlebar stem is attached to the steerer shaft, the handlebar is attached to the handlebar stem.
In a threadless system, the steerer shaft is sufficiently long so as to protrude through the upper end of the head tube. The lower bearing is disposed between the fork crown and the lower end portion of the head tube. The upper bearing is disposed between upper end portion of the head tube carrying an upper cone or cup. The handlebar stem is directly attached to the upper end portion of the steerer shaft. The handlebar is then attached to the steerer shaft.
As you will note in the prior art, the handlebar/handlebar stem is always directly attached to or is supported by the steerer shaft which extends through the head tube of the bicycle frame. Such configuration is not optimal in the structural and aerodynamic sense because the load bearing steerer shaft must be sized smaller than the bore through the frame such that it can rotate freely.
The frontal area of a bicycle contributes to the amount of aerodynamic drag that a cyclist experiences. The bicycle front end is the initial part of the bicycle/rider unit that slices through the air. On one hand, if the bicycle front end slices through the air efficiently, then the amount of drag that the cyclist would have to overcome is reduced. On the other hand, if the bicycle front end slices through the air inefficiently, then the amount of drag that the cyclist would have to overcome is increased.
In bicycle sport racing, it is advantageous to reduce the amount of drag because less drag equates to a faster race time. The front end assembly of prior art bicycles is prone to drag due to the discontinuous shape thereof and the fact that the frame's head tube must be necessarily have a larger frontal area than is required to fit the fork steerer shaft, which bears the steering loads, into the head tube. Preferably, the steerer shaft is very stiff in torsion and bending. This can be achieved by increasing the moment of inertia of said steerer shaft. Accordingly, there is a need in the art for a more aerodynamically shaped bicycle front end assembly.